Noma A, Irisawa H
Pflugers Arch. 1976 Jun 29;364(1):45-52. doi: 10.1007/BF01062910.
When a strand of the rabbit sinoatrial node tissue was shortened by ligation, the spatial decay of electrotonic potential decreased and the input impedance increased. In a piece of the tissue 0.2-0.3 mm in diameter apparently uniform current spread was obtained. Action potentials recorded from three different sites in this small piece occurred simultaneously and were superimposable. In voltage clamp experiments using the double microelectrode method, the membrane potential was usually held at -30 to -40 mV, where no net current flowed. When membrane potential was suddenly changed from the holding potential, the sign and the time course of the ionic current varied with membrane potential. Hyperpolarization gave an inward current which increased with time. Depolarization gave a transient inward current followed by sustained outward current, and repolarization gave an outward current tail which exponentially subsided with a time constant of 0.37 s. The membrane time constant was 12.0 ms. When the specific membrane capacitance was assumed to be 1 muF/cm2, the specific membrane resistance at the resting potential was 12 Komega cm2. The peak of the transient inward current on depolarization was 1.3 X 10(-5) A/cm2.
当兔窦房结组织的一条束状结构通过结扎缩短时，电紧张电位的空间衰减减小，输入阻抗增加。在直径为0.2 - 0.3毫米的一块组织中，获得了明显均匀的电流分布。从这块小组织中三个不同部位记录到的动作电位同时出现且可叠加。在使用双微电极法的电压钳实验中，膜电位通常保持在 -30至 -40 mV，此时无净电流流动。当膜电位突然从保持电位改变时，离子电流的方向和时间进程随膜电位而变化。超极化产生一个随时间增加的内向电流。去极化产生一个短暂的内向电流，随后是持续的外向电流，复极化产生一个外向电流尾，其以0.37秒的时间常数呈指数衰减。膜时间常数为12.0毫秒。当假定比膜电容为1 μF/cm² 时，静息电位下的比膜电阻为12 KΩ·cm²。去极化时短暂内向电流的峰值为1.3×10⁻⁵ A/cm²。
